Manufacturing apparatus for metal molded body

ABSTRACT

There is provided a manufacturing apparatus for a metal molded body. The manufacturing apparatus includes: a die having an elongated shape in plan view; and a plurality of pairs of thrust units disposed along a wall surface with the die disposed therebetween from both sides of the die, wherein the pairs of thrust units have electromagnetic coils that generate reverse traveling magnetic fields, and the pairs of thrust units arranged in a longitudinal direction are set so as to generate the reverse traveling magnetic fields for each series composed of a single thrust unit or a plurality of the thrust units.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a manufacturing apparatus for a metal molded body. More specifically, the present invention relates to an apparatus for suppressing growth of a metal crystal by electromagnetically stirring melted metal such as aluminum alloy, cooling the melted metal while discharging residual gas as a source of a mold cavity, and producing a tough metal molded body.

Description of Related Art

Description will be made by taking an example of aluminum as metal. In order to produce a precise aluminum material, it is essential that aluminum as a material has a fine crystal structure, and does not have defects such as a mold cavity therein. In order to produce such a material, molten aluminum is transferred to a die of a stirrer (manufacturing apparatus for a metal molded body), and growth of a crystal structure is prevented by stirring and cooling the molten aluminum in the die, so that a dense material is produced. Mechanical force is sometimes used as stirring force, but an electromagnetic force method capable of performing stirring in a non-contact manner is preferable in consideration of abrasion and the like of a stirring rod.

In order to perform stirring by electromagnetic force, a large number of coils are arranged along a wall surface (indicating an inner wall surface) of the die, a magnetic field which travels along the wall surface by a group of these coils is formed. An induced current is generated in the molten aluminum by the traveling magnetic field, electromagnetic force (Lorentz force) is generated by the current and the changing magnetic field, and the molten metal moves along the wall surface. Then, the movement of the molten metal along the wall surface reaches the center, so that stirring as a whole proceeds. This stirring work is continued until the metal is solidified. There are a case where the solidified metal is used as a final molded body with no change, and a case where the solidified metal is transposed to a press forming die to be pressurized and formed. The aluminum material thus completed has strong strength, and has less defects such as a mold cavity. Therefore, such an aluminum material is reliable as a part material.

In general, in an aluminum rabble furnace, a molten substance is stirred in a cylindrical melting pot, as described in JP 5352236 B1, JP 2009-74103 A, and JP 2007-144501 A. Therefore, the electromagnetic stirring apparatus has a cylindrical shape, similarly to a motor stator. However, for example, in a case where an elongated structure is made of aluminum, the shape of a stirring die is elongated. In the cylindrical rabble furnace, the volume of the furnace becomes huge, and huge excitation force is required, which is irrational. Therefore, a linear type stirring apparatus described in JP 2006-289448 A is known.

As a structure of a thrust section of a linear type stirring apparatus, JP 2006-289476 A, “Electromagnetic Coil Designed by Magneto-Hydro-Dynamic Simulation”, shinnittetsu giho vol. 379, and “Development of a Simulation Model for Electromagnetic Stirring in Melting Furnace, Furukawa-sky Review” No. 3, 2007” are known.

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

A vehicle body structure and the like are generally thin and long. In addition, such structures are often bent. Accordingly, in the circular stirring apparatus, as described above, the furnace volume is large, and excitation force (AT) for operation becomes extremely strong, and therefore handling is difficult. Therefore, such a linear type stirring apparatus described in JP 2006-289448 A, and JP 2006-289476 A, related to a continuous casting apparatus is applied. However, the linear type stirring apparatus has an elongated structure, and has a long acceleration distance (refer to FIG. 1). Such a long acceleration distance increases the speed of molten metal, and a phenomenon that the molten metal runs on a wall surface of a die at a folded part or turning position having a small radius of curvature (refer to an end 18 of FIG. 1), or runs over the wall surface to fall to the outside is generated. In particular, the die is provided with a draft angle, and therefore the molten metal more easily runs on the wall surface.

In order to suppress such a run-over phenomenon, when excitation force is reduced, traveling becomes moderate, and the run-over is suppressed. On the other hand, stirring efficiency is lowered, and a metal molded body formed of fine crystals cannot be efficiently manufactured. The present invention solves such a problem, and an object of the present invention is to provide a manufacturing apparatus for a metal molded body capable of performing efficient stirring by using an elongated die, and suppressing run-on or run-over of molten metal to a die wall surface.

Means to Solve the Problem

A manufacturing apparatus for a metal molded body of the present invention includes: a die having an elongated shape in plan view; and a plurality of pairs of thrust units disposed along a wall surface with the die disposed therebetween from both sides of the die, wherein the pairs of thrust units have electromagnetic coils that generate reverse traveling magnetic fields with each other and the thrust units arranged in a longitudinal direction are set so as to generate reverse traveling magnetic fields for each single thrust unit or each series composed of a plurality of the thrust units.

Such a manufacturing apparatus for a metal molded body may include a control circuit that switches the traveling magnetic fields of the electromagnetic coils such that the thrust units arranged in the longitudinal direction generate the reverse traveling magnetic fields for each desired number of the thrust units. Additionally, a whole or a part of the die may be curved in plan view. Furthermore, the manufacturing apparatus for a metal molded body preferably includes a thrust unit that causes an obliquely vertical traveling magnetic field, in addition to the thrust unit that causes a horizontal traveling magnetic field.

Effect of the Invention

In the manufacturing apparatus for a metal molded body of the present invention, a partial circulation flow of molten metal can be generated in the die by the traveling magnetic fields of the series composed of a pair of or a plurality of pairs of the thrust units disposed along the wall surface with the die disposed therebetween. That is, a flow in one direction is generated by the single or the plurality of thrust units disposed along one wall surface, and a flow in the other direction is generated by the single or the plurality of thrust units disposed along the other wall surface. Then, in an end of each series, a flow is generated in the die crossing direction. Therefore, a flow that circulates for each thrust unit is generated. The traveling direction of the magnetic field of a certain series of the thrust units, and the traveling direction of the magnetic field in the other series of the thrust units adjacent to the certain series of the thrust units are reversed from each other, and therefore the directions of the circulation flows are reversed. For example, when a clockwise circulation flow is generated in the series of the pair of thrust units, a counterclockwise circulation flow is generated in the other series of pair of thrust units in the adjacent to the series of the pair of thrust units.

Therefore, in each of the ends of the series of the thrust units, the flow along the wall surface is divided, and a node is formed in the flow. Therefore, an accelerated flow reduces the speed at a portion of the node or joint, and migration energy is converted into stirring energy. Therefore, running on the wall surface and running over the wall surface are suppressed. Additionally, at the portion of the node, the molten metal flowing from one of both sides collides with the molten metal flowing from the other side, or is divided, and therefore the molten metal is more efficiently stirred.

In a case where such a manufacturing apparatus for a metal molded body includes the control circuit that switches the directions of the traveling magnetic fields of the electromagnetic coils such that the thrust units arranged in the longitudinal direction generate the reverse traveling magnetic fields for each desired number of the thrust units, suitable stirring action and flow rate can be selected in accordance with the kind of metal. In a case where the die is curved in plan view, the curved metal molded body can be efficiently produced, and suppression of the above run-on and run-over can be attained similarly to the above.

In a case where the manufacturing apparatus includes the thrust unit that causes the obliquely vertical traveling magnetic field, in addition to the thrust unit that causes the horizontal traveling magnetic field, molten metal obliquely flows, and therefore a laminar flow commutates, and can be more efficiently stirred, and crystal grains can be made fine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a plan view illustrating a manufacturing apparatus for a metal molded body according to an embodiment of the present invention, and FIG. 1B is an enlarged view of an essential part.

FIG. 2 is a II-II line sectional view of the manufacturing apparatus of FIG. 1A.

FIG. 3A and FIG. 3B are a schematic plan view and a schematic side view illustrating thrust units according to an embodiment (core back winding method) of the present invention, respectively.

FIG. 4A and FIG. 4B are a schematic plan view and a coil connection diagram illustrating thrust units according to another embodiment (slot winding method) of the present invention, respectively.

FIG. 5 is a plan view illustrating an example of wire connection when a plurality of the thrust units of FIG. 3A and FIG. 3B are combined.

FIG. 6 is a plan view illustrating a manufacturing apparatus for a metal molded body according to another embodiment of the present invention.

FIG. 7A and FIG. 7B are a front view and a plan view illustrating thrust unit that changes a flow of molten metal according to an embodiment of the present invention, respectively (illustration of the shapes of coil sides are omitted).

FIG. 8A to FIG. 8D each are a plan view illustrating a manufacturing apparatus for a metal molded body according to yet another embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A manufacturing apparatus (electromagnetic stirring apparatus) 10 for a metal molded body illustrated in FIG. 1A includes an elongated die 11 that is curved in an arc shape in plan view, and a plurality of pairs of thrust units 12 that are disposed along a wall surface of the die with the die disposed therebetween. Each thrust unit 12 includes cores 13, and coils 14 that are wound around the cores 13, as illustrated in FIG. 1B. In this embodiment, two sets each obtained by winding the three coils 14 around the one core 13 are connected through a wedge shaped magnetic body 15 for curvature adjustment at an angle, and are made to be one unit. In FIG. 1A, the wedge shaped magnetic bodies are omitted.

The die 11 has a substantially U-shaped cross-section including a bottom plate 16, and side walls 17 rising from both ends of the bottom plate, as illustrated in FIG. 2, for example. In general, the depth of the die 11 is deeper than the width. Additionally, the side walls 17 are provided with draft angles, and expand toward upper ends. The die 11 is formed of metal having heat resistance enough to withstand a high temperature of molten metal, and having low magnetic permeability (for example, stainless steel), ceramics, or the like. The thrust units 12 are obliquely disposed in parallel to the wall surface with slight gaps G between the wall surface (inner wall surface) of the inclined side walls 17 and the thrust units 12.

The size and the shape of the die 11 depend on the size and the shape of a member to be molded. As illustrated in FIG. 1A, ends 18 of the die 11 each have an arc shape such that the direction of molten metal can be smoothly changed. In this embodiment, the right and left side walls 17 are each curved. The right and left side walls 17 have a common center of the curvature, and have almost the same width in the length direction. The thrust units 12 disposed along the side walls 17 are disposed so as to be curved or bent similarly, gaps G (refer to FIG. 2) with the side walls (inner side walls) 17 are as small as possible, and are constant along the longitudinal direction.

FIG. 3A and FIG. 3B each illustrate a thrust unit 12 by a “core back wounding method” among a basic shape. Each thrust unit 12 includes the core 13 having a comb-tooth shape, and the coils 14 that are wound between teeth of the core. The core 13 is composed of a rectangular column shaped yoke (core back) 19, and teeth 21 having ends fixed to dovetail-shaped grooves 20 formed in the yoke. The number of the teeth 21 is seven, the number of the coils 14 to be wound around the yoke between the teeth is six, and all the coils are wound in the same direction. Therefore, in a case where a current enters from an initially wound coil, and a case where a current enters from a finally wound coil, the polarities are reverse. Slots 22 between the teeth 21 are filled with the coils (coil conductors) 14. The slots 22 are opened toward the die 11 through slits 23 that are elongated openings. The yoke 19 and the teeth 21 are each formed by superimposing a large number of thin sheets of silicon steel sheets. The yoke and the teeth may be integrated.

FIG. 4A and FIG. 4B illustrates a thrust unit 12A by “inter-slot winding method” among a basic shape. In this method, the thrust unit 12A includes the core 13 having a comb-teeth shape including the yoke 19 and a plurality of the teeth 21, and the coils 14 each wound around a plurality of the teeth 21. The slots 22 a to 22 f are filled with the coils (coil conductors) 14. The coils 14 are composed of three kinds of coils 14 u, 14 v, 14 w corresponding to a U-phase, a V-phase, and a W-phase of three-phase current (AC), respectively. A U-phase coil 14 u passes through a leftmost slot 22 a and a fourth slot 22 d to be wound around three teeth between the leftmost slot and the fourth slot.

Similarly, a V-phase coil 14 v passes through a third slot 22 c and a sixth slot 22 f to be wound around three teeth between the third slot and the sixth slot. A W-phase coil 14 w passes through a second slot 22 b and a fifth slot 22 e to be wound around three teeth between the second slot and the fifth slot. These three kinds of coils 14 u, 14 v, 14 w are overlapped to be intersect with each other on the lateral side of the core 13, as illustrated in FIG. 4B. Symbol 0 denotes a neutral point of a three-phase current. In the thrust unit 12A by such an “inter-slot winding method”, the coils 14 u to 14 w are not wound the core back 19, and therefore the core back 19 can be used to fix the thrust unit.

FIG. 5 illustrates wire connection in which three thrust units 12 are lined on one side of the die 11. A power source is a three-phase current. Symbol 0 is a neutral point. When three-phase current U, W, V are sequentially connected to coils of terminal symbols R, S, T, a magnetic flux advances from the left to the right (refer to an arrow φ1). When a phase order is changed and the three phase current are connected to the U-phase, the V-phase, the W-phase in order, a magnetic flux advances from the right to the left (the arrow φ2 direction). That is, in FIG. 5, in a left end unit 12 a, the W-phase is connected to a winding finish end of a coil denoted by symbol w1−, and the V-phase is connected to a winding start end of a coil denoted by symbol v1+. In an central unit 12 b, the V-phase is connected to a winding finish end of a coil denoted by symbol w3−, the W-phase is connected to a winding start end of a coil denoted by symbol v3+, the V-phase and the W-phase are reverse. Furthermore, connection in a right end unit 12 c is similar to the connection in the left end unit 12 a, and therefore a magnetic flux advances in the arrow φ3 direction similar to the arrow φ1.

When such thrust units are disposed on both side of a pot, as illustrated in FIG. 6, the advancing directions of magnetic fluxes of units 12 a, 12 b, 12 c on the near side of the die 11 and the advancing directions of magnetic fluxes of units 12 d, 12 e, 12 f on the far side are made reverse. Consequently, in a case where the direction of a vortex Q1 of molten metal caused by a pair of the left end units 12 a, 12 d is counterclockwise, a clockwise vortex Q2 is generated in a pair of the central units 12 b, 12 e. Furthermore, a counterclockwise vortex Q3 is generated again in a pair of the right end units 12 c, 12 f.

Therefore, the directions of the circulating vortexes are reverse for each set of the adjacent units, and therefore in the ends of the thrust units, a flow along the wall surface is divided, so that nodes 24 a, 24 b are formed in the flow. Therefore, an accelerated flow reduces the speed at portions of the node 24 a and node 24 b, and migration energy is converted into stirring energy. Therefore, also when molten metal flows into the arc shapes of the ends, or also when the side walls 17 are curved as illustrated in FIG. 1A, running onto the wall surface of the side walls 17, and running over the side walls 17 are suppressed. Additionally, at the portions of the node 24 a and the node 24 b, the molten metal flowing from one of the both sides collides with the molten metal flowing from the other side, and furthermore, an integrated flow is divided, and therefore the molten metal is more efficiently stirred.

In the embodiment, the thrust units are arranged in parallel to the inner side walls of the die (means that a void is uniform), a vortex generates horizontally. However, for example, as illustrated in FIG. 7A and FIG. 7B, a thrust unit 25 that generates a vertically inclined flow P can be combined. Two slots 22 of the thrust unit 25 are formed with slits 23 provided with an inclined angle (skew) which retreats toward the lower part. By such skew, a vertical oblique flow P generates in the molten metal, and a laminar flow of the molten metal in the die commutates. Therefore residual gas venting is facilitated, more efficient stirring is attained, and therefore it is possible to make crystal grains fine.

Such skew can be formed by obliquely machining the slits 23, when electromagnetic steel plates are stuck to perform machining on the slots 22 by wire cutting. The slots 22 are filled with the coils (coil conductor) 14, but are omitted in FIG. 7B. Reference numeral 26 in FIG. 7B denotes a wedge or plate for holding the coils 14 in the slot 22.

In the embodiment, the advancing direction of the magnetic field is reversed for each thrust unit 12, and the direction of vortexes Q1, Q2 of molten metal are reversed for each pair of the thrust units 12 as illustrate in FIG. 8A. However, the two or three thrust units as illustrated in FIG. 8B and FIG. 8C, or the four or more thrust units as illustrated in FIG. 8D can form a “series” in which the advancing direction of a magnetic field is the same, and can be installed such that the vortexes are reversed for each series. In this case, the number or nodes are reduced, and therefore stirring action is reduced, but the speed of each vortex is increased. Accordingly, suitable stirring action and vortex speed can be set in accordance with the kind of metal to be manufactured.

Furthermore, a control circuit that switches, for each thrust unit, the direction of a current that flows into electromagnetic coils of the thrust unit may be provided, and the direction of the traveling magnetic field may be changed for every arbitrary n thrust units such as every single thrust unit, and every two thrust units, and the directions of vortexes may be able to be reversed. In such a manufacturing apparatus for a metal molded body capable of changing wiring of the coils of the thrust units, suitable stirring action and vortex speed can be selected in accordance with the kind of metal, and a metal molded body can be efficiently manufactured. 

1. A manufacturing apparatus for a metal molded body, the manufacturing apparatus comprising: a die having an elongated shape in plan view; and a plurality of pairs of thrust units disposed along a wall surface with the die disposed therebetween from both sides of the die, wherein the pairs of thrust units have electromagnetic coils that generate reverse traveling magnetic fields, and the thrust units arranged in a longitudinal direction are set so as to generate reverse traveling magnetic fields for each single thrust unit or each series composed of a plurality of the thrust units.
 2. The manufacturing apparatus for a metal molded body according to claim 1, comprising a control circuit that switches directions of traveling magnetic fields of the electromagnetic coils such that the thrust units arranged in the longitudinal direction generate reverse traveling magnetic fields for each desired number of the thrust units.
 3. The manufacturing apparatus for a metal molded body according to claim 1, wherein a whole or a part of the die is curved in plan view.
 4. The manufacturing apparatus for a metal molded body according to claim 2, wherein a whole or a part of the die is curved in plan view.
 5. The manufacturing apparatus for a metal molded body according to 1, further comprising a thrust unit that causes an obliquely vertical traveling magnetic field, in addition to the thrust unit that causes a horizontal traveling magnetic field.
 6. The manufacturing apparatus for a metal molded body according to 2, further comprising a thrust unit that causes an obliquely vertical traveling magnetic field, in addition to the thrust unit that causes a horizontal traveling magnetic field.
 7. The manufacturing apparatus for a metal molded body according to 3, further comprising a thrust unit that causes an obliquely vertical traveling magnetic field, in addition to the thrust unit that causes a horizontal traveling magnetic field.
 8. The manufacturing apparatus for a metal molded body according to 4, further comprising a thrust unit that causes an obliquely vertical traveling magnetic field, in addition to the thrust unit that causes a horizontal traveling magnetic field. 